The invention relates to a method for controlling the stability of simple water-in-oil emulsions, and to stabilize simple water-in-oil emulsions.
Emulsions are compositions, usually liquid or gelled, comprising at least two phases which are not miscible, one phase being dispersed in the form of droplets into the other. Using emulsifiers allows obtaining the dispersion of one of the phases in the other. Thus, emulsions are usually obtained by mixing the phases and emulsifiers with adding energy, for examples by vigorously mixing and/or heating. The nature and the amount of the emulsifier, and the nature and the amount of each phase are parameters in emulsions art. These parameters usually have an influence on the droplets size, the quantity of droplets emulsified, the stability, the energy to be added for emulsifying.
Direct emulsions, essentially consisting of a hydrophobic phase dispersed in an aqueous phase, and water-in-oil emulsions, essentially consisting of an aqueous phase dispersed in a hydrophobic phase, are known. These two types of emulsions are usually considered as two different technical fields, since different phases are usually used, as well as different emulsifiers (nature and amounts). Simple emulsions and multiple emulsions are also known. Multiple emulsions consist for example of three phases system wherein an internal emulsion comprising a first phase dispersed in a second phase is dispersed as droplets in a third external phase. In such emulsions the first and the third phase may be the same, being separated by the second phase. Simple emulsions consist of an internal phase being dispersed in an external phase, wherein the internal phase does not further comprises a liquid phase dispersed therein. Simple and multiples emulsions are also considered as different art, since problems to be addressed are different. The invention relates to simple water-in-oil emulsions.
Controlling the droplets size and the stability of emulsions (i.e. avoiding demixion coalescence, flocculation and/or creaming) is an issue to be addressed for many purposes. In consumer goods, there is a need for emulsions to have a long lifetime, as well for it to keep its properties as for it to keep a good aspect. Examples of consumer goods comprising simple water-in-oil emulsions are cosmetics compositions such as make-up, and skin-care creams, for example sunscreens, and more particularly waterproof sunscreens . . . Simple water-in-oil emulsions are also used in the field of explosive products. Stability a particularly important property in that field. Other fields wherein simple water-in-oil emulsions are used include some anti-foaming compositions used in paper industry; water-in-oil emulsion polymerization, fracturing fluids used in oil fields, vehicles diesel gas (green diesel).
There is a need for new emulsifiers or emulsifier mixtures, that would provide an emulsification (droplets size) and/or a stability as good as and/or better than those of current emulsifiers or emulsifier mixtures, for some different phases or at different conditions, for example at higher temperatures.